RFR(S): 8024368: private methods are allocated vtable slots

[dean.long at oracle.com]

It sounds like the vtable slot was there for backwards compatibility, 
but I don't understand how a vtable slot for a private method ensured 
compatibility (how does it affect behavior?), so I don't understand how 
we continue to ensure backwards compatibility without it.  Also, which 
tests check for the desired backwards compatibility?

dl

On 10/19/18 9:43 AM, serguei.spitsyn at oracle.com wrote:
> Hi Karen and Lois,
>
> I have just one official review from David.
> May I count your internal reviews as official?
> Do we need the Compiler team to review this as well?
>
> Thanks,
> Serguei
>
> On 10/16/18 18:29, David Holmes wrote:
>> Bizarre!
>>
>> Looks good - officially Reviewed again!
>>
>> Thanks for fixing Serguei!
>>
>> David
>>
>> On 17/10/2018 4:34 AM, serguei.spitsyn at oracle.com wrote:
>>> Re-sending my RFR.
>>> Behive managed not to deliver it to the target mailing lists.
>>> David got it because he was on the cc-list.
>>>
>>>
>>> Please, review a fix for:
>>> https://bugs.openjdk.java.net/browse/JDK-8024368
>>>
>>> Webrev:
>>> http://cr.openjdk.java.net/~sspitsyn/webrevs/2018/8024368-priv-vtable.2/ 
>>>
>>>
>>>
>>> Summary:
>>>
>>>    Private method should not allocate vtable indeces.
>>>    The fix tweaks several conditions in the functions:
>>> klassVtable::update_inherited_vtable() and 
>>> klassVtable::needs_new_vtable_entry(),
>>>    adds a couple of asserts and makes several comments up-to-date.
>>>
>>>    The fix was preliminary reviewed by Karen, David H. and Lois.
>>>
>>> Testing:
>>>
>>>    The fix was verified with 
>>> runtime/{appcds+Nestmates+RedefineTests+SelectionResolution}
>>>    and vmTestbase/vm/runtime/defmeth tests.
>>>    Also, I ran a mach5 job with the flags: 
>>> tier1,tier2,hs-tier3,hs-tier4,hs-tier5.
>>>
>>>    By suggestion from David, it was also tested with the -Xlog 
>>> output for vtables before and after the fix.
>>>    I've done this comparison (awk was used to get rid of the first 
>>> column with the time stamps).
>>>    It shows that private methods were included into vtable before 
>>> the fix but not included after.
>>>    Please, see one fragment as an example:
>>>
>>>     166c166
>>>     <  copy vtable from java.lang.Object to java.lang.StackFrameInfo 
>>> size 17
>>>     ---
>>>     >  copy vtable from java.lang.Object to java.lang.StackFrameInfo 
>>> size 16
>>>     180d179
>>>     <  adding 
>>> java.lang.StackFrameInfo.ensureRetainClassRefEnabled()V at index 16, 
>>> flags: private
>>>     182c181
>>>     <  copy vtable from java.lang.StackFrameInfo to 
>>> java.lang.LiveStackFrameInfo size 17
>>>     ---
>>>     >  copy vtable from java.lang.StackFrameInfo to 
>>> java.lang.LiveStackFrameInfo size 16
>>>     188,201c187,191
>>>     <  copy vtable from java.lang.Object to 
>>> java.lang.StackStreamFactory$AbstractStackWalker size 18
>>>     <  adding 
>>> java.lang.StackStreamFactory$AbstractStackWalker.close()V at index 
>>> 5, flags: private
>>>     <  adding 
>>> java.lang.StackStreamFactory$AbstractStackWalker.toStackWalkMode(Ljava/lang/StackWalker;I)I 
>>> at index 6, flags: private
>>>     <  adding 
>>> java.lang.StackStreamFactory$AbstractStackWalker.consumeFrames()Ljava/lang/Object; 
>>> at index 7, flags: protected abstract
>>>     <  adding 
>>> java.lang.StackStreamFactory$AbstractStackWalker.initFrameBuffer()V 
>>> at index 8, flags: protected abstract
>>>     <  adding 
>>> java.lang.StackStreamFactory$AbstractStackWalker.batchSize(I)I at 
>>> index 9, flags: protected abstract
>>>     <  adding 
>>> java.lang.StackStreamFactory$AbstractStackWalker.getNextBatchSize()I 
>>> at index 10, flags: protected
>>>     <  adding 
>>> java.lang.StackStreamFactory$AbstractStackWalker.skipReflectionFrames()Z 
>>> at index 11, flags: private
>>>     <  adding 
>>> java.lang.StackStreamFactory$AbstractStackWalker.doStackWalk(JIIII)Ljava/lang/Object; 
>>> at index 12, flags: private
>>>     <  adding 
>>> java.lang.StackStreamFactory$AbstractStackWalker.getNextBatch()I at 
>>> index 13, flags: private
>>>     <  adding 
>>> java.lang.StackStreamFactory$AbstractStackWalker.beginStackWalk()Ljava/lang/Object; 
>>> at index 14, flags: private
>>>     <  adding 
>>> java.lang.StackStreamFactory$AbstractStackWalker.fetchStackFrames(I)I 
>>> at index 15, flags: private
>>>     <  adding 
>>> java.lang.StackStreamFactory$AbstractStackWalker.fetchStackFrames(JJII[Ljava/lang/Object;)I 
>>> at index 16, flags: private native
>>>     <  adding 
>>> java.lang.StackStreamFactory$AbstractStackWalker.callStackWalk(JIII[Ljava/lang/Object;)Ljava/lang/Object; 
>>> at index 17, flags: private native
>>>     ---
>>>     >  copy vtable from java.lang.Object to 
>>> java.lang.StackStreamFactory$AbstractStackWalker size 9
>>>     >  adding 
>>> java.lang.StackStreamFactory$AbstractStackWalker.consumeFrames()Ljava/lang/Object; 
>>> at index 5, flags: protected abstract
>>>     >  adding 
>>> java.lang.StackStreamFactory$AbstractStackWalker.initFrameBuffer()V 
>>> at index 6, flags: protected abstract
>>>     >  adding 
>>> java.lang.StackStreamFactory$AbstractStackWalker.batchSize(I)I at 
>>> index 7, flags: protected abstract
>>>     >  adding 
>>> java.lang.StackStreamFactory$AbstractStackWalker.getNextBatchSize()I 
>>> at index 8, flags: protected
>>>
>>>
>>> Thanks,
>>> Serguei
>>>
>